A guide wire is employed to guide a catheter used for treatment of a region where surgical operation is difficult, for treatment where low-level intervention into the human body is desired, for inspection in cardiovascular contrast imaging and the like. For example, when PCI (Percutaneous Coronary Intervention) is performed, with the guide wire positioned so that its distal end is projecting from the distal end of a balloon catheter, the guide wire is inserted, under radioscopy, to a location in proximity to a constricted portion of a coronary artery which is a target region to guide the distal end portion of the balloon catheter to the location in proximity to the constricted portion.
An example of a guide wire for use with such treatment is described in U.S. Pat. No. 5,797,857. This guide wire includes a wire body (core member) having flexibility, a coil (X-ray contrast imaging metal coil) disposed so as to cover the outer periphery of the distal end portion of the wire body, and a coating layer (synthetic resin coating member, hydrophilic lubricating layer) for covering the outermost surface of the wire body and the coil.
When the guide wire disclosed in U.S. Pat. No. 5,797,857 is used to perform such an operation as described above, depending upon the state of the coronary artery such as the degree of the curvature of the coronary artery, a phenomenon such as described below sometimes occurs.
For example, if the guide wire is pushed in when the coil of the guide wire is positioned at (inserted in) a sharply bent portion of a coronary artery, excessive force (of such a degree that plastic deformation occurs) is sometimes applied to the coil. In this instance, part of a strand which forms the coil sometimes rides on an adjacent strand portion to cause plastic deformation of the coil. Therefore, there is the possibility that the coil may not be restored to its ordinary (normal) state and the pushing-in force from the proximal end portion of the wire body may not be transmitted with certainty to the distal end portion of the wire body through the coil. That is, the pushing-in performance may be significantly deteriorated.
Further, although the hydrophilic lubricating layer is provided on the coil of the guide wire of U.S. Pat. No. 5,797,857, depending upon the thickness of the guide wire, for example, when the distal end portion of the guide wire is positioned at (inserted in) a sharply bent portion of a coronary artery, comparatively high frictional resistance appears between the hydrophilic lubricating portion at the distal end portion and the bent portion described hereinabove. In other words, the hydrophilic lubricating layer at the distal end portion sometimes sticks to the bent portion. Therefore, there is the possibility that, even if torque is applied from the proximal end portion of the wire body, the torque may not be transmitted with certainty to the distal end portion of the wire body. That is, the torque transmission performance may be significantly deteriorated.